In recent years fire protection devices, known as smoke detectors or smoke alarms, have been developed. These devices, especially a type known as the ionization type of smoke detector, are very effective in sensing the airborne products of combustion at an early stage in the development of a fire. The device then activates a sounding device to warn persons in the vicinity of impending danger.
Smoke alarms, in general, have a limited area of effective monitoring and are ordinarily intended for use in dwellings, for example, in the hall of a house having bedrooms adjoined thereto. Certain types of these alarms may be employed in multiples for use in larger households, wherein they may be interconnected so that if one unit detects smoke, all of the alarm units are activated for warning all the occupants of the house. Generally, those smoke alarms which are designed for the above described interconnected use have an accessible socket for interconnection thereto, since fire regulations for such devices generally discourage connection to the internal circuitry of the detector-alarm unit.
It has been found on the multiple pin socket that certain pins have an electrical output thereon when the smoke alarm is triggered by detection of smoke. This output is the driving power for the sounding device and may be measured as a voltage with a current delivery capability. It has also been found that the interconnection of certain pins of the socket will cause the sounding device to be activated in the absence of smoke.
The present invention is a network of such smoke alarm units, connected with a control panel and including switching members, that makes use of the socket conditions of the above described type of smoke alarm unit. The network of the present invention is a two-way system in that the smoke alarm units communicate alarm signals to the control panel while switch members on the control panel are operable to send alert signals to the smoke alarm units.